The present invention relates to a relief/check valve construction particularly useful with land vehicle and marine fuel systems.
In certain fuel supply systems it is often desirable to use an anti-siphon valve in the fuel supply line from the fuel tank to the carburetor. This valve is essentially a relief valve which opens when the fuel pump operates to permit uni-directional flow from the tank to the carburetor. When the pump ceases, the valve closes against the fuel head in the tank to prevent the fuel in the tank from being siphoned to the carburetor where it can leak into the engine compartment. One of the problems which has been observed with the use of an anti-siphon valve concerns fuel expansion in the carburetor. Since the relief valve prevents reverse flow to the tank, the expanding fuel can only overflow the carburetor, thereby causing several problems, such as fire hazard, undesirable vapor emissions, potential engine flooding, etc. Since the preferred relief valve previously used for fuel line anti-siphon purpose is dimensionally compact, it initially appeared that the problem of fuel expansion could not be solved without complicating the fuel supply circuit or increasing the size of the anti-siphon valve.
One of the objects of the present invention, therefore, is to provide an improved relief/check valve which, when utilized as an anti-siphon valve for a fuel supply system, solves the aforementioned problem without increasing either the size of the previous anti-siphon valve or the complexity of the fuel supply circuit, and yet which will handle the requisite flow rates.
In another aspect, the present invention is applicable to an improvement in fuel tank vent valves. Prior fuel tank vent valves are essentially normally closed relief/check valves which open under pre-determined conditions to prevent vacuum or excessive pressure in the fuel tank. The check valve element opens to let air enter the tank as fuel is withdrawn, and the relief valve element opens to vent the tank to atmosphere when the fuel vapor pressure becomes too high. One of the problems with prior fuel tank vent valves is that they do not provide adequate safety in the event of a vehicle crash which crushes the fuel tank. In such an event, it is possible for the crushing of the tank to raise the pressure therein to relatively high pressures (e.g. 15, psi or greater), which results in liquid fuel escaping in large quantities via the vent valve. This problem is aggravated in the case of aluminum fuel tanks, which barrier tests have shown to collapse more readily than steel tanks.
Another object of the present invention, therefore, is to provide an improved relief/check valve which is particularly suited for use as a fuel tank vent valve, but which avoids the aforementioned leakage problems to which aluminum fuel tanks are particularly subject.
The present invention solves the aforementioned problems without adversely increasing the size of and with only minimal revision to presently available valves. The valves according to the present invention provide reliable operation at minimum cost and hence are well suited for mass production applications.
Additional objects, features, advantages, and benefits of the invention will be seen in the ensuing description and claims, which are to be taken in conjunction with the accompanying drawing. The drawing illustrates several preferred embodiments of the invention in accordance with the best modes presently contemplated for carrying out the invention.